High prevalence of osteonecrosis of the femoral head in anti-MDA5 antibody-positive dermatomyositis

BACKGROUND: Osteonecrosis of the femoral head (ONFH) is a serious and not uncommon complication in several autoimmune diseases. There is limited research and understanding of ONFH in idiopathic inflammatory myopathies (IIM). AIM: To investigate the prevalence, clinical characteristics and predictive factors of ONFH in IIM. DESIGN: An observational cohort study. METHODS: We retrospectively enrolled 1464 IIM patients, who were classified into ONFH and non-ONFH groups. Independent predictors of ONFH were identified by logistic regression and incorporated into a prediction model. Model performance was assessed using receiver operating characteristic curve, the Hosmer-Lemeshow test, calibration curves and decision curve analysis. RESULTS: The prevalence of ONFH was 5.9% (86/1464) in IIM. Notably, almost half (52.3%, 45/86) tested positive for anti-melanoma-differentiation-associated gene 5 (MDA5) antibodies in patients with ONFH. Pulse or high-dose glucocorticoids (>1 mg/kg/d) (G) (OR: 2.857, 95% CI: 1.769-4.613), anti-MDA5 antibodies (A) (OR: 3.546, 95% CI: 2.140-5.876), muscle weakness (M) (OR: 1.968, 95% CI: 1.154-3.356), periungual erythema (P) (OR: 2.198, 95% CI: 1.229-3.931) and hyperlipidemia (H) (OR: 4.784, 95% CI: 2.827-8.095) were identified as independent risk factors for ONFH. To better predict ONFH, a nomogram model was constructed, demonstrating good discrimination with an AUC of 0.798 (95% CI: 0.747-0.849). For rapid risk assessment, a simplified scoring model was developed and designated as 'GAMPH', with an AUC of 0.797 (95% CI: 0.747-0.848). CONCLUSIONS: ONFH is not a rare complication of IIM, particularly among patients positive for anti-MDA5 antibodies. This study provides a promising clinical tool for identifying IIM patients at risk of developing ONFH.